Evaluation of a Microfluidic Mixer Utilizing Staggered Herringbone Channels: A Computational Fluid Dynamics Approach

Microfluidic platforms offer a variety of advantages including improved heat transfer, low working volumes, ease of scale-up, and strong user control on parameters. However, flow within microfluidic channels occurs at low Reynolds numbers, which makes mixing difficult to accomplish. Adding V-shaped ridges to channel walls, a pattern called the staggered herringbone design (SHB), might alleviate this problem by introducing transverse flow patterns that enable enhanced mixing. However, certain factors affecting the SHB mixer’s performance remain largely unexplored.In this work, a microfluidic mixer utilizing the SHB geometry was developed and characterized using computational fluid dynamics based simulations and complimentary experiments. A channel design with SHB ridges was simulated in COMSOL Multiphysics under a variety of operating conditions to evaluate its mixing capabilities. The device was fabricated using soft-lithography to experimentally observe the mixing process. The mixing was visualized by pumping fluorescent dyes through the device and imaging the channels using a confocal microscope.The device was found to efficiently mix fluids rapidly, based on both simulations and experiments. Varying the Reynolds number or component diffusion coefficients had a weak effect on the mixing profile, due to the laminar flow regime and insufficient residence time, respectively. Mixing effectiveness decreased as the component flow rate ratio increased. Fluid flow patterns visualized in confocal microscope images were highly identical to the simulated results, suggesting that the simulations serve as good predictors of the device’s performance. This SHB mixer design would be a good candidate for further implementation as a reactor